Daily encounters with verbal information are both visual (i.e., reading text) and auditory (i.e., spoken language comprehension). Research has established that as we age, we become less efficient readers. Compared with reading comprehension, however, much less is known about how listening comprehension is affected by aging. To fill this gap in the literature, we propose to conduct the first large-scale study of the determinants of age-related differences in listening comprehension across the adult life span by testing a sample of 490 adults between the ages of 20 and 90 years. Specifically, this study will examine four potential mediators (hearing acuity, processing speed, working memory, and speech perception) of the relationship between age and listening comprehension, all of which are strongly associated with deficits in older adults. The major goal of our study will be to determine whether these mediators affect age-related deficits in listening comprehension directly or indirectly and to evaluate the relative contributions of these variables using structural equation modeling. As part of our modeling efforts, we will evaluate both the linear and non-linear effects of age. By determining the best-fitting causal model of the data, we will be able to shed light on the theoretical mechanisms underlying age-related differences in listening comprehension and, at the same time, identify where rehabilitative efforts can be most effectively directed. This project represents a unique opportunity to explore the nature of listening comprehension and the dynamics of aging on performance by bringing expertise to focus on this issue from the areas of cognitive processing, the psychology of aging, general speech perception, and aural rehabilitation. [unreadable] [unreadable]